JPS6140962Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic drive system, and more particularly to a hydraulic drive system used in a vehicle having a crawler-type or wheel-type traveling device.

Conventionally, as a device applicable to such a hydraulic drive system of a vehicle, for example, the devices described in Japanese Utility Model Application Publication No. 1988-8884, Japanese Patent Application Publication No. 47-16878, and Japanese Patent Application Publication No. 50-16231 These devices include a hydraulic motor, a pair of supply/discharge passages for supplying and discharging high-pressure oil to the hydraulic motor, and operating the supply of high-pressure oil to the supply/discharge passages to operate the hydraulic motor. forward rotation, reverse rotation,
A directional control valve that controls stopping, a brake that applies a brake to the rotating shaft of the hydraulic motor when high pressure oil is not supplied to the brake cylinder and releases the brake when high pressure oil is supplied to the brake cylinder, and a supply/discharge path. The high-pressure selection valve selects the high-pressure side pressure oil and supplies it to the brake cylinder of the brake.

In these devices, when the directional control valve is in the neutral position (hydraulic motor stop position), the high pressure selection valve and the oil tank are communicated via the supply/discharge path, and the high pressure selection valve and the brake are in communication. The passageway connecting the brake cylinder has a structure that allows oil to quickly flow from the high pressure selection valve toward the brake cylinder.

Therefore, when these conventional devices are applied to hydraulic drive devices such as crawler vehicles, it is necessary to increase the brake capacity to ensure safety, which causes the problem that the brake becomes larger and costs increase. It was hot. That is, when a crawler vehicle or the like operates a brake to stop and then drives a shovel or the like to perform work, the engine of the vehicle is generally operated to rotate a pump that supplies oil to the supply/discharge passage. In this case, a directional control valve disposed between the pump and the high-pressure selection valve is usually placed in a neutral position so that oil supplied from the pump to the supply/discharge path is returned to the oil tank via the directional control valve. on the other hand,
There is circuit resistance in the directional switching valve and the passage connecting the directional switching valve and the oil tank. Therefore, even when such a directional control valve is in the neutral position, the supply/discharge path has a certain pressure (so-called back pressure) due to the circuit resistance, and this pressure is applied to the valve member of the high-pressure selection valve. It is communicated with the brake cylinder through the sliding gap of the ball and spool, and acts in the direction of releasing the brake. Therefore, the brake needs to have a large capacity that can obtain sufficient braking torque so as not to be affected by this pressure (back pressure). Further, in general, the rotation of an engine fluctuates periodically and uneven rotation occurs. Due to the periodic rotational fluctuations and rotational irregularities of this engine,
Periodic rotational fluctuations and rotational irregularities occur in the pump, and the amount of oil supplied from the pump to the supply/discharge path also fluctuates periodically and irregularly. Therefore, the pressure (back pressure) in the supply and exhaust passage during parking also fluctuates periodically and irregularly, so the brake must be sufficiently strong so that it is not affected by these oil pressure (back pressure) fluctuations. It must have a large capacity that can generate torque. Furthermore, when the engine is revved up, the number of rotations of the pump increases rapidly, and the amount of oil discharged and the back pressure increase rapidly. The brake needs to have a large capacity so that it will not be released even for a moment even when such a sudden increase in back pressure occurs. This is because if the brake is released even for a moment, the vehicle will descend down the slope and the safety of the work will be compromised, such as when the vehicle is stopped on a slope for work.

The present invention has been made in view of the above points, and includes a hydraulic motor, a pair of supply and discharge passages that supply pressure oil from a hydraulic source to the hydraulic motor and discharge oil discharged from the hydraulic motor into an oil tank. A parking brake that applies a brake to the rotating shaft of the hydraulic motor when pressure oil is not supplied and releases the brake on the rotating shaft of the hydraulic motor when pressure oil is supplied, and a parking brake that is placed in the middle of a pair of supply and discharge passages. a high-pressure selection valve that communicates with the oil tank through a selection passage; a shuttle valve that is provided in the middle of the selection passage and communicates with the oil tank through a drain passage; a switching valve that communicates the pair of supply and discharge passages on the high pressure selection valve side with the oil tank in the neutral position, and communicates the hydraulic power source with the oil tank;
The high-pressure selection valve supplies pressurized oil from a high-pressure side supply/discharge passage to the parking brake, and the shuttle valve communicates with a first port that communicates with the high-pressure selection valve through a selection passage and with the parking brake through a selection passage. a second port, a third port that communicates with the oil tank through a drain passage; and when pressure oil is supplied to the first port from the high pressure selection valve and is biased by a spring to close the first port, the first port and the second port are connected to supply pressure oil to the parking brake, and when the pressure oil from the high pressure selection valve to the first port is cut off, the second port and the third port are connected to supply pressure oil to the parking brake. A hydraulic drive device for a vehicle characterized by having a valve body for returning oil to an oil tank.

(Operation) When the switching valve is in the neutral position, oil supplied from the hydraulic source is returned to the oil tank via the switching valve, and the parking brake is activated. At this time, back pressure is generated due to resistance in the switching valve and the circuit from the switching valve to the oil tank, and this back pressure attempts to be transmitted to the parking brake through the supply/discharge path, the high pressure selection valve, and the selection passage. However, a shuttle valve is provided in the selection passage, and the valve body of this shuttle valve is biased by a spring to prevent communication between the back pressure fluid and the parking brake (to close the first port). Therefore, the back pressure is not transmitted to the parking brake. Additionally, when the back pressure overcomes the biasing force of the spring, oil flows from the valve body side (first port side) of the shuttle valve to the parking brake and oil tank side (second port and third port side).
(port side). This leakage amount is due to an increase in back pressure, so it is extremely small, and since it is returned to the oil tank through the third port, it is essentially
No pressure increase occurs on the second and third port sides, and therefore no action to release the parking brake occurs. By releasing this small amount of oil, the shuttle valve again shuts off the back pressure fluid and the parking brake. In addition, this back pressure fluctuates periodically or irregularly due to changes in the vehicle's engine rotation, but similar to the above-mentioned effect, this back pressure is blocked by the shuttle valve and the parking brake is activated. is not transmitted. When a sudden increase in back pressure occurs due to rapid rotational fluctuations in a vehicle's engine, and this back pressure overcomes the spring force of the shuttle valve, the same effect as described above occurs when a small amount of oil on the first port side is It is returned to the oil tank via the third port, and does not substantially release the parking brake. Therefore, it is possible to prevent the parking brake from being released even for a moment without increasing the capacity of the parking brake.

An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1, 2, and 3, 20 is a brake valve, and the case 21 of this brake valve 20 is
A spool-type switching valve 22 and a brake load valve 23 are provided inside. Among these, the spool-type switching valve 22 includes a spool 25 inserted into a sleeve 24 and slidably provided to the case 21 via the sleeve 24, and two check valves built in the center of the spool 25. valve 26,2
6', two damper check valves 27, 27' built into the end of the spool 25, and the spool 25.
Cushion dampers 28, 28' are provided opposite both ends of the spool 25, and the washer 2 is mounted on the spool 25.
9, 29' and cushion damper 2.
8, 28' to hold the spool 25 in the neutral position. This sleeve 24 is held in the case 21 by caps 31, 31' via cushion dampers 28, 28'.
Alternatively, it has a so-called cartridge structure in which the sleeve 24 and the spool 25 can be taken out together by removing the sleeve 31'. The check valves 26, 26' are
The damper check valves 27, 27' are pressed against the seat surface in the spool 25 by springs 32, 32', and the damper check valves 27, 27' are also pressed against the seat surface in the spool 25 by springs 33, 33'. The other brake load valve 23 includes a sleeve 34 inserted into the case 21 and a hollow shuttle valve 35 slidably provided in the center of the sleeve 34.
and seat surfaces 35a, 3 of this shuttle valve 35.
5a' with two relief valves 37, 37' pressed by springs 36, 36', and inserted into bodies 38, 38' at positions opposite to the outside of the relief valves 37, 37'. It is supported within the sleeve 34 and is supported on the seat surface 3 by springs 39, 39'.
8a, 38a' and pilot valves 40, 40' which are crimped onto the pilot valves 8a, 38a'. The sleeve 34 of the brake load valve 23 is bolted to the case 21 through bodies 38, 38', and by removing the bodies 38, 38', the sleeve 34 can be taken out and the shuttle valve 35, relief valve 37, 3
7' and pilot valves 40, 40' can be removed. The relief valves 37, 37' have small holes 37a, 37 in their heads.
a' is formed and communicates with the shuttle valve 35 to introduce high pressure oil to the tips of the pilot valves 40, 40'. Further, the springs 39, 39' of the pilot valves 40, 40' can be adjusted by adjusting screws 41, 41'.
Lock nuts 42, 42' and cap nuts 4
3 and 43' for detent fixation.
The relief valves 37 and 37' are provided with a slight stroke margin in order to completely press the shuttle valve 35 and the heads of the relief valves 37 and 37'. In order to restrict sliding, stoppers 38b, 38b' are provided near the relief valves 37, 37'.
Inside the case 21, there are provided ports 44, 44' and 45, 45' through which pressure oil flows in or out, and ports 46, 47, 47' through which pressure oil flows out. Passages 48, 48' communicating with the spool type switching valve 22
and 49, 49', spool type switching valve 2
2 and the brake load valve 23.
0, 50', a passage 51, 51' communicating between the ports 45, 45' and the brake load valve 23, a passage 52 communicating between the ports 47, 47' and the pilot valve 40, 40', 52', one end of which is closed by the land of the spool 25 when the spool 25 is in the neutral position, and is closed by the land of the spool 25 when the spool 25 moves in either the left or right direction.
A passage 53 is provided which communicates with one of the high-pressure oil side passages 8' and whose other end communicates with the port 46. Note that the passages 51 and 51' are connected to the sleeve 3.
4 communicates with the passages 50, 50' by an annular passage on the outside.

Outside the brake valve 20 explained above,
As shown in FIG. 3, the ports 44, 44' of the brake valve 20 are
a pump 64 connected to the switching valve 62 via a passage 63; and an oil tank 66 connected to the switching valve 62 via a passage 65.
and a passage 67 connecting the pump 64 and the oil tank 66.
and a first port 70 that can communicate with a hydraulic motor 69 connected to the ports 45 and 45' of the brake valve 20 via a pair of passages 68 and 68', respectively.
a, second port 70b, and third port 70c
The spring 70 is configured to cut off communication between the first port 70a and the second port 70b and communicate between the second port 70b and the third port 70c when high pressure oil is not introduced into the first port 70a.
d maintains the switching position of the valve 70e, and when high pressure oil is introduced into the first port 70a, the first port 70
a and the second port 70b are connected to each other, and the second port 70
a valve 70 that cuts off communication between b and the third port 70c;
eShuttle valve 70 in switching position and port 4
6 and the first port 70a of the shuttle valve 70, a parking brake 73 connected to the second port 70b of the shuttle valve 70 via a passage 72, and a spring 74 in which the brake is applied. The rotation shaft 75 of the hydraulic motor 69 provided and one end connected to the ports 47, 4
7', a drain passage 7 whose other end is connected to an oil tank 66;
6, 76', a drain passage 77 having one end connected to the hydraulic motor 69 and the other end to the oil tank 66, and a drain passage 78 having one end connected to the third port 70c of the shuttle valve 70 and the other end to the oil tank 66. , is provided. The aforementioned passages 48, 48', 50, 5
0'51, 51', 61, 61', 63, 65, 6
7, 68, 68' collectively constitute a pair of supply/discharge passages 79, 79' for supplying and discharging pressure oil to the hydraulic motor 69. In addition, the aforementioned passages 53, 71, 72
As a whole, a selection passage 80 is connected to the switching valve 22 at one end and the parking brake 73 at the other end. Further, the switching valve 22 is communicated with the parking brake 73 through a selection passage 80, and the supply/discharge passage 7
A high-pressure selection valve is configured to select the high-pressure side hydraulic pressure of 9 and 79' and supply it to the shuttle valve 70.

Next, the operation of one embodiment of the present invention will be explained.

1, 2, and 3, first, the operation of the brake valve 20 when high pressure oil flows in from the port 44 will be described. In this case, as shown in FIG. 3, the switching valve 62 is set to the switching position 62a, the pump 64 is operated to draw up and pressurize oil from the oil tank 66, and the pressurized high-pressure oil is passed through the switching valve 62 to the switching position 62a. Supply to port 44 of valve 20.
The high pressure oil flowing from this port 44 flows into the passage 48.
The liquid passes through the air, hits the check valve 26, pushes the check valve 26 open against the spring 32, and flows into the passage 50. The high pressure oil that has flowed into the passage 50 is
1, flows out of the brake valve 20 from the port 45, and flows through the passage 68 to the hydraulic motor 69.
is supplied to the hydraulic motor 69, and acts to apply a force in the rotational direction to the hydraulic motor 69. Further, the high pressure oil flowing from the port 44 passes through the passage 49 and hits the damper check valve 27.
7 is pushed open against the spring 33 and flows into the chamber 28a formed by the cushion damper 28 and the end face of the spool 25. The high-pressure oil that has flowed into this chamber 28a acts on the diametrical cross-sectional area of the spool 25 as a hydraulic load cross-sectional area, causing the spool 25 to move towards the spring 3.
0', and by this movement of the spool 25, the spool type switching valve 22 is moved as shown in FIG.
It functions to switch to the switching position shown at 2a. During this movement of the spool 25, the damper check valve 27' on the opposite side to the oil outflow side remains closed, so that the oil in the chamber 28a' formed by the cushion damper 28' and the end face of the spool 25 is kept closed. The spool 25 and cushion damper 28'
It is throttled through the gap 28b' and flows out to the port 44' through the passage 49', acting to buffer the moving speed of the spool 25, that is, the switching speed of the spool-shaped switching valve 22. In addition, the switching valve 2
2 is at the switching position 22a, the supply/discharge path 7
9' opens, the return oil from the hydraulic motor 69 flows through the passage 68', the port 45', the passage 51', and the passage 5.
0', passage 48' and port 44' to the switching valve 62, through which it is returned to the oil tank 66. Moreover, when the spool type switching valve 22 is at the switching position 22a,
The passage 48 and the passage 53 are in communication, and the port 44 and the port 46 are in direct communication, and the selected high-pressure oil is delivered to the shuttle valve 7 through the passages 53 and 71.
0 to the first port 70a of the shuttle valve 7.
It communicates with the first and second ports 70a and 70b of No. 0. The high-pressure oil that has passed through the shuttle valve 70 is supplied into the parking brake 73 through a passage 72, and is applied against the spring 74.
This acts to loosen the brake caused by the hydraulic motor 69, allowing the rotary shaft 75 of the hydraulic motor 69 to freely rotate. At this time, the hydraulic motor 69 is activated by the parking brake 73.
It is released from the brake and starts rotating, and continues to rotate from then on.

Next, the operation of the brake valve 20 when the inflow of high pressure oil from the port 44 is stopped will be described. In this case, as shown in FIG.
is in the neutral switching position 62b, the oil discharged by the pump 64 is short-circuited in the switching valve 62 and returned to the oil tank 66 without load, and the ports 44 and 44' of the brake valve 20 are connected in the oil tank 66. Short-circuiting eliminates the supply of high pressure oil to the brake valve 20. In this way, when the inflow of high pressure oil from port 44 is stopped, spool 25
The 0' force difference causes the spool-shaped switching valve 22 to be moved toward the center of the case 21 and automatically returns to the neutral state, ie, the switching position shown at 22b in FIG. 3. At this time, the hydraulic motor 69 continues to rotate due to the inertia of the load.
9 starts functioning as a pump, and as a result, oil is sucked into the hydraulic motor 69 from the port 45.
At the same time, high pressure oil is supplied to the port 45' to the hydraulic motor 69.
It is discharged from. Among these, the high pressure oil discharged from the hydraulic motor 69 is blocked from the passage 50' and the passage 48' because the check valve 26' is closed and the spool type switching valve 22 is at the switching position shown by 22b. Therefore, the pressure in the passages 50' and 51' is high, and the shuttle valve 3 of the brake load valve 23 is
5 to the passage 50 side until it hits the stopper 38b. By this movement of the shuttle valve 35,
The seat portion of one relief valve 37' is opened, and the seat portion of the other relief valve 37 remains closed, and the high pressure oil in the passages 50' and 51' flows into the shuttle valve 35, and the small hole 37a , 37a' into the relief valves 37, 37' and act to pressurize the pilot valves 40, 40'. The hydraulic pressure to the pilot valves 40, 40' is applied to the spring 3.
9, 39', the pilot valves 40, 40' open and the relief valve 3 opens.
The oil in the drain passages 76, 76' flows out into the passages 52, 52' and is led to the oil tank 66 from the ports 47, 47' through the drain passages 76, 76'. At this time, the small holes 37a, 3
The back pressure of the relief valves 37, 37' decreases due to the throttling action of 7a', and the relief valves 37, 37'
6 and 36', and one of the relief valves 37, which had been closed, opens. This relief valve 3
7 opens, the passages 51 and 50 communicate with the passages 51' and 50', and the ports 45 and 45' communicate with each other, and the high pressure oil from the hydraulic motor 69 flows through the port 45' and the passage. 51', the shuttle valve 35, the passage 51 and the port 45, and are sucked into the hydraulic motor 69 again. In addition, by further opening the other relief valve 37', which was open, the opening area with the shuttle valve 35 increases, and the resistance to oil inflow decreases, making it easier for oil to be relieved. In addition to the above, the oil sucked into the hydraulic motor 69 is caused by the check valve 26 opening against the spring 32 due to negative pressure in the passages 50 and 51;
The oil flows from the oil tank 66 through the port 44, passage 48, passage 50, passage 51, and port 45, and the insufficient oil is replenished. Also,
When the spool type switching valve 22 returns to the switching position 22b shown in FIG.
There is no communication between ports 44 and 46, and there is no communication between port 46 and shuttle valve 7.
The supply of oil to the first port 70a of 0 is stopped,
Communication between the first port 70a and the second port 70b of the shuttle valve 70 is cut off by the urging force of the spring 70d, and the second port 70a of the shuttle valve 70
0b and the third port 70c communicate with each other. For this reason,
The oil in the parking brake 73 cannot oppose the spring 74, and flows out into the drain passage 78 through the second and third ports 70b, 70c of the shuttle valve 70, and is returned to the oil tank 66. When the oil in the parking brake 73 flows out, the rotation shaft 75 of the hydraulic motor 69 is braked by the force of the spring 74. The braking by the parking brake 73 is applied to the hydraulic motor 69 following absorption of the rotational load of the hydraulic motor 69 by the brake load valve 23 described above.
It acts effectively to stop the Furthermore, when the brake is activated to stop the crawler vehicle and drive a shovel or the like, the pump 64 is being rotated and oil is supplied from the pump 64 to the passage 63.
Since the switching valve 62 is in the neutral position while the vehicle is stopped, oil supplied from the pump 64 to the passage 63 is discharged to the oil tank 66 through the switching valve 62 and the passage 65. However, the switching valve 62 and the passage 65 have circuit resistance, and in particular, the passage of the switching valve 62 is narrow and has a large circuit resistance. Due to this circuit resistance, passage 6
1 and the passage 48 (so-called back pressure), which is transmitted to the passage 80 via the gap in the oil passage of the high-pressure selection valve 22. This back pressure acts in the direction of releasing the parking brake 73.
However, the shuttle valve 70 is disposed in the middle of the passage 80, and the shuttle valve 70 is
e is biased by a spring 70d and blocks the first port 70a and the second port 70b.
Therefore, the back pressure due to the circuit resistance is cut off by the shuttle valve 70, and the parking brake 7
3 is not transmitted. When the back pressure overcomes the urging force of the spring 70d, oil leaks from the first port 70a side to the second port 70b and third port 70c via the valve 70e. This amount of leakage is due to an increase in back pressure, so it is extremely small, and the third port 70c is connected to the drain passage 7.
Since the parking brake 73 is connected to the oil tank 66 which is open to the atmosphere through the oil tank 8, the parking brake 73 is maintained at atmospheric pressure. By releasing this small amount of oil, the shuttle valve 70 again shuts off the first port 70a and the second and third ports 70b and 70c. Also, fluctuations in back pressure due to periodic fluctuations or irregular fluctuations in the engine speed are blocked by the shuttle valve 70 and are not transmitted to the parking brake 73. moreover,
Even when the back pressure increases rapidly due to engine revving, etc., and this back pressure overcomes the biasing force of the spring 70d, the first port 70a
Since a small amount of oil on the side is released into the oil tank 66 through the third port 70c, virtually no oil pressure fluctuations are transmitted to the parking brake 73, and the parking brake 73 is not released even for a moment.
Therefore, the capacity of the parking brake 73 can be reduced, reducing costs, and even if the vehicle is stopped on a slope to perform work, the vehicle will not descend down the slope, improving work safety. can be ensured. The operation of the brake valve 20 when high pressure oil flows in from port 44 and then stops flowing is described above, but high pressure oil flows in from port 44' and further stops flowing. In this case, the brake valve 20 operates in the same manner as described above, except that the rotation direction of the hydraulic motor 69 is reversed.

As explained above, according to the present invention, when the switching valve is in the neutral position, the shuttle valve interposed between the high pressure selection valve and the parking brake is moved by the spring in the direction of blocking the first port and the second port. Since the second port is energized and the second port is connected to the oil tank through the third port, when the vehicle is stopped with the engine running, back pressure due to circuit resistance and its fluctuations are not transmitted to the parking brake, and the parking brake is activated. It will never be released even for a moment. Therefore, work safety can be ensured, the capacity of the parking brake can be reduced, and costs can be reduced.

[Brief explanation of the drawing]

The drawings show an embodiment of the hydraulic drive device according to the present invention, in which Fig. 1 is a sectional view of the brake valve, Fig. 2 is an explanatory diagram of the structure of the brake valve, and Fig. 3 is indicated by JIS symbols. FIG. 22 is a high pressure selection valve (switching valve), 66 is an oil tank, 6
9 is a hydraulic motor, 70 is a shuttle valve, 70a is a first port, 70b is a second port, 70c is a third port
Port, 70d is spring, 70e is valve, 73
75 is a parking brake, 75 is a rotating shaft, 78 is a drain passage, 79 and 79' are supply/discharge passages, and 80 is a selection passage.

Claims (1)

[Scope of utility model registration request] A hydraulic motor and a pair of supply/discharge passages for supplying pressure oil from a hydraulic source to the hydraulic motor and discharging oil discharged from the hydraulic motor to an oil tank, and applying a brake to the rotating shaft of the hydraulic motor when pressure oil is not supplied. A parking brake that releases the brake on the rotating shaft of the hydraulic motor when pressure oil is supplied, a high-pressure selection valve that is disposed midway between a pair of supply and discharge passages and communicates with the parking brake through a selection passage, and a high-pressure selection valve that is placed midway through the selection passage. A shuttle valve is provided in the tank and communicates with the oil tank through a drain passage, and the pair of supply and discharge passages on the high pressure selection valve side are arranged in the pair of supply and discharge passages between the hydraulic power source and the high pressure selection valve and are connected to the oil tank in the neutral position. and a switching valve that communicates with the hydraulic source and the oil tank, the high pressure selection valve supplies pressurized oil in the high pressure side supply/discharge passage to the parking brake, and the shuttle valve supplies the high pressure selection valve with pressurized oil in the supply/discharge path on the high pressure side. A first port that communicates with the parking brake through a selection passage, a second port that communicates with the parking brake through a selection passage, a third port that communicates with the oil tank through a drain passage, and a first port that communicates with the parking brake through a selection passage.
When the port is biased to close and pressure oil is supplied from the high pressure selection valve to the first port, the first port and the second port are communicated to supply pressure oil to the parking brake, and the pressure oil is supplied from the high pressure selection valve to the parking brake. A hydraulic drive device for a vehicle, comprising: a valve body that communicates the second port and the third port and returns the parking brake pressure oil to the oil tank when the pressure oil to the first port is cut off. .